Tire information detecting device

ABSTRACT

A tire information detecting device includes detecting means for detecting a state quantity in a tire, transmitting means for transmitting a signal outputted from the detecting means, receiving means for receiving the signal transmitted from the transmitting means, the receiving means mounted at a vehicle body side, and a brake actuator adjusted to apply a braking force to the vehicle. The receiving means is positioned at a radially inner side from a major diameter of the brake actuator.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119with respect to a Japanese Patent Application 2003-283537, filed on Jul.31, 2003, the entire content of which is incorporated herein byreference.

FIELD OF THE INVENTION

This invention generally relates to a tire information detecting device.More particularly, this invention pertains to a tire informationdetecting device, the receiving unit of which can reliably receive anoutput signal of a transmitting unit disposed on a wheel supporting atire.

BACKGROUND

Conventionally, a tire information receiving device, which receives asignal outputted from a transmitting unit mounted at a tire wheelwithout being in contact with the transmitting unit, has been widelyknown. A type of this tire information receiving device is disclosed inJP9(1997)-240228A2. In this device, one end of a stay member is fixed toa hub at a vehicle side. One end of a stay member is equipped at theother end of the stay member. A receiving part is fixed at the other endof the stay member. As described above, the receiving part 5 issupported by the cantilevered stators that are fixed to the vehiclestationary portion. Further, the receiving part is mounted so as to beadjacent to an inner diameter portion of the tire wheel.

In a tire information receiving device which receives information of atire state quantity such as an air pressure outputted from atransmitting part mounted at a disc wheel, recent developments have leadto stabilizing information receiving response and to developing mountingposition and method of the receiving device so as to reduce themanufacturing cost.

A need exists for providing a tire information detecting device capableof reliably detecting information such as a tire air pressure.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a tire informationdetecting device includes detecting means for detecting a state quantityin a tire, transmitting means for transmitting a signal outputted fromthe detecting means, receiving means for receiving the signaltransmitted from the transmitting means, the receiving means mounted ata vehicle body side, and a brake actuator adjusted to apply a brakingforce to the vehicle. The receiving means is positioned at a radiallyinner side from a major diameter of the brake actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the presentinvention will become more apparent from the following detaileddescription considered with reference to the accompanying drawings,wherein:

FIG. 1 is a block view illustrating a tire information detecting deviceapplied for a vehicle control system according to an embodiment of thepresent invention;

FIG. 2 is a view illustrating a receiving unit mounted at a vehicle sideaccording to the embodiment of the present invention;

FIG. 3 is a cross sectional view illustrating a position of thereceiving unit of the tire information detecting device mounted in thevicinity of a disc wheel according to the embodiment of the presentinvention;

FIG. 4 is another cross sectional view illustrating the position of thereceiving unit when the disc wheel mounted with the transmitting unit isequipped for a vehicle driven wheel;

FIG. 5A is a view illustrating a conventional structure in which thetransmitting unit is fixed at the disc wheel and the receiving unit isfixed at a tire housing side;

FIG. 5B is a characteristic view for explaining a variation of a signalreceiving response of the receiving unit fixed at the tire housing side;

FIG. 6A is a view illustrating a structure in which the transmittingunit is fixed at the disc wheel and the receiving unit is mounted at aradially inner side from a major diameter of a brake actuator accordingto the embodiment of the present invention; and

FIG. 6B is a characteristic view for explaining a variation of a signalreceiving response of the receiving unit mounted at the radially innerside from the major diameter of the brake actuator.

DETAILED DESCRIPTION

An embodiment of the present invention will be described hereinbelow indetail with reference to the accompanying drawings.

As illustrated in FIG. 1, a tire information detecting device WIS isprovided with a transmitting unit TU (i.e., transmitting means) mountedat or on a disc wheel DW (illustrated in FIG. 3) for a driving sidevehicle wheel and a receiving unit RU (i.e., receiving means) mounted ata vehicle (main) body side. The transmitting unit TU includes adetecting unit DU (i.e., detecting means) for detecting a tire pressureand a tire temperature, each of which can be a parameter to directlydetect a state quantity in a tire T. Therefore, the transmitting unit TUis adjusted to transmit the state quantity detected by the detectingunit DU to the receiving unit RU. The transmitting unit TU furtherincludes a modulating circuit MC (i.e., signal modulating means) formodulating a signal associated with the detected state quantity, and atransmitting antenna TA for actually transmitting the modulated signalto an exterior portion. According to the embodiment of the presentinvention, the detecting unit DU detects the tire pressure and the tiretemperature. However, the detecting unit DU can be added with functionsfor detecting a vehicle wheel acceleration and for detecting a powersupply voltage supplied to the detecting unit DU.

The receiving unit RU includes a receiving antenna RA for receiving asignal transmitted from the transmitting unit TU, a signal demodulatingcircuit DC (i.e., signal demodulating means) for demodulating thereceived signal, a vehicle wheel speed sensor SS for detecting a vehiclewheel speed, and a signal processing circuit SMC for feeding the signalsfrom the signal demodulating circuit DC and the vehicle wheel speedsensor SS to a vehicle system control unit VCU. According to theembodiment of the present invention, a widely used signal wire connectsthe vehicle system control unit VCU with the signal processing circuitSMC, whereby information can be transmitted between the vehicle systemcontrol unit VCU and the signal processing circuit SMC.

The transmitting antenna TA of the transmitting unit TU transmits theinformation such as the tire pressure and the tire temperature to thereceiving unit RU at a predetermined time distance. In this case, inorder to transmit the information detected by the detecting unit DU tothe receiving unit RU, the signal representing the state quantity of thevehicle tire T is modulated by the modulating circuit MC. Asnon-limiting examples, the information fed from the transmitting antennaTA to the receiving unit RU corresponds to several types of frequenciesappropriately set following vehicle types. Each of the frequencies canbe 315 MHz, 433 MHz, 868 MHz, or the like. The frequencies to be appliedfor the tire information detecting device WIS do not have to be limitedto the above and can be anything as far as they are defined in afrequency band recognized for each vehicle type.

According to the embodiment of the present invention, communicationcycles between the transmitting unit TU and the receiving unit RU aredefined independently pursuant to a vehicle stationary condition, avehicle driving condition, and a vehicle abnormal condition. Moreparticularly, while the vehicle has been under the stationary condition,it is sufficient to perform the communication therebetween only one timefor a few hours. However, while the vehicle has been under the abnormalcondition, it is preferable to control the communication therebetween tobe performed at least once per second. The communication cycle isindependently set in response to a condition of a vehicle system. Thecommunication therebetween can be carried on in a manner that thereceiving unit RU requests the transmitting unit TU to transmit thesignal to the receiving unit RU, in a manner that the transmitting unitTU regularly transmits the signal to the receiving unit RU, or the like.The information (the signal) received by the receiving unit RU isdemodulated by the signal demodulating circuit DC and is generated as asignal possessing tens of kilohertz of low frequency. The signalprocessing circuit SMC digitalizes the signal having the low frequencyand transmits the digitalized signal to the vehicle system control unitVCU.

As illustrated in FIG. 2, the receiving unit RU is mounted at thevehicle side according to the embodiment of the present invention. Thereceiving unit RU is positioned at a radially inner side relative to amajor diameter of a brake disc BD (i.e., a brake actuator), i.e., withina range corresponding to a diameter of the brake disc BD. The receivingunit RU is then fixed at a knuckle arm KA (i.e., a linking member) at avehicle side. The knuckle arm KA is supported by a suspension (notillustrated). According to the embodiment of the present invention, thebrake disc BD corresponds to the brake actuator. Alternatively, a drumbrake can correspond to the brake actuator.

As illustrated in FIG. 3, the transmitting unit TU having the detectingunit DU is mounted on or near the disc wheel DW. The transmitting unitTU is positioned in a space defined between an outer peripheral surfaceof the disc wheel DW and the tire T and is fixed to an intermediateposition of the disc wheel DW. The intermediate position is definedapproximately halfway of an axial dimension of the disc wheel DWextending substantially along a drive shaft DS. The drive shaft DS isconnected to an inner hub IH. The brake disc BD is also connected to theinner hub IH. That is, the drive shaft DS, the inner hub IH and thebrake disc BD are integrally connected by bolts B. The brake disc BD isjointed to the inner hub IH via the bolts B. Therefore, the disc wheelDW rotates substantially integrally with the drive shaft DS. Further, anouter hub OH is disposed surrounding the inner hub IH. There are pluralhub bearings HB disposed between the inner hub IH and the outer hub OH,thereby allowing relative rotation therebetween. The outer hub OH issubstantially integrally fixed to the knuckle arm KA. The hub bearingsHB do not allow rotational force of the inner hub IH to be transmittedto the outer hub OH.

As described above, the knuckle arm KA is attached with the receivingunit RU. The receiving unit RU includes the receiving antenna RA, thesignal demodulating circuit DC and the vehicle wheel speed sensor SS(i.e., vehicle wheel speed detecting means), all of which are integrallymolded with resin. According to the embodiment of the present invention,a sensor with a Hall element is applied as the vehicle wheel speedsensor SS. Therefore, the rotational speed of the disc wheel DW can beobtained by the vehicle wheel speed sensor SS which detects a magneticfield generated in response to rotation of a rotor R. The rotor R isdisposed between the inner hub IH and the outer hub OH. According to theembodiment of the present invention, the vehicle speed sensor SS isintegrally formed at the receiving unit RU. Therefore, the number ofcomponents can be decreased. A manufacturing cost of the receiving unitRU, i.e., a manufacturing cost of the tire information detecting deviceWIS hence may be able to be effectively reduced. Further, an assemblingman-hour may be able to be effectively reduced. Needless to say, thevehicle wheel speed sensor SS can be connected to the receiving unit RUvia a connector.

As described above, when the receiving unit RU is mounted at the knucklearm KA for the vehicle wheel, the receiving unit RU is positioned at theradially inner side from the major diameter of the brake actuator. Inthis case, the vehicle wheel is driven with a force transmitted from anengine via a transmission.

FIG. 4 illustrates a positional relationship between the inner hub IHand the receiving unit RU at a time that the disc wheel DW with thetransmitting unit TU is attached to a vehicle driven wheel. In thiscase, the space established at a time that the disc wheel DW with thetransmitting unit TU is attached to a vehicle drive wheel as illustratedin FIG. 2, the space in which the drive shaft DS is positioned, is notestablished herein. Therefore, the receiving unit RU is disposed at anarea substantially corresponding to a radial directional length of theinner hub IH, i.e., in the vicinity of the inner hub IH as illustratedin FIG. 4.

Next, following description will be given for describing a variation ofa signal receiving response depending upon the mounting positions of thetransmitting unit TU and the receiving unit RU with reference to FIGS.5A, 5B, 6A and 6B.

When the vehicle runs, the signal receiving response of the receivingunit RU is explained depending upon each case where the transmittingunit TU is positioned at either A, B, C or D point, with reference toFIGS. 5B and 6B. According to the embodiment of the present invention,the receiving unit RU is positioned inside of the diameter direction ofthe brake actuator, i.e., in the vicinity of a rotational center of thetire T. Therefore, even if the transmitting unit TU rotates followingthe rotation of the tire T, a distance between the transmitting unit TUand the receiving unit RU does not vary so that the receiving responsecan be effectively prevented from fluctuation. That is, a distancebetween the transmitting unit TU and the receiving unit RU can bemaintained at a substantially constant distance value regardless of therotational position of the transmitting unit TU following the rotationof the tire T. As explained in FIGS. 5B and 6B, a stabilized signalreceiving response can be obtained according to the structureillustrated in FIG. 6A.

If the receiving unit TU is not supported at a member such as theknuckle arm KA or the inner hub IH, but is supported by a cantileveredmember, the receiving unit TU may be influenced by vibration applied atthe cantilevered member. In this case, the receiving response of thereceiving unit TU may fluctuate due to the vibration. Further, thecantilevered member may be damaged due to the vibration, wherein areliability of this receiving device is not assured. Further, a mountingmember may be required for fixing the receiving unit TU at thecantilevered member such that the number of components are increased andthe assembling hours are also increased.

According to the embodiment of the present invention, the transmittingunit TU and the receiving unit RU are mounted in order to definepolarized waves of the units TU and RU approximately in parallel with arotational shaft of the tire T, respectively. In this case, a polarizedarea and directional characteristics of the receiving antenna RA can bemaintained at a constant value even when the transmitting unit TUrotates, thereby enabling to obtain further preferable signal receivingresponse.

Further, according to the embodiment of the present invention, amagnetic field component of the wave transmitted from the transmittingunit TU is designed to be approximately in parallel with a rotationalshaft of the tire T. Therefore, the polarized area in the respondingdirection of the receiving antenna RA can be approximately orthogonallyoriented relative to the rotational shaft of the tire. That is, thereceiving antenna RA is arranged to have the highest precision insensing the magnetic field component of the wave transmitted from thetransmitting unit TU. In this case, the polarized wave area anddirectional characteristics of the receiving antenna RA can beeffectively maintained at a constant value relative to the rotatingtransmitting unit TU, thereby enabling to obtain further preferablereceiving response.

The principles, the preferred embodiment and mode of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiment disclosed. Further,the embodiment described herein is to be regarded as illustrative ratherthan restrictive. Variations and changes may be made by others, andequivalents employed, without departing from the spirit of the presentinvention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims, be embracedthereby.

1. A tire information detecting device comprising: a detector whichdetects an air pressure in a tire; a transmitter which transmits asignal outputted from the detector; a receiver which receives the signaltransmitted from the transmitter, the receiver being mounted at avehicle body side; and a brake disc adjusted to apply a braking force toa vehicle, wherein the receiver is positioned radially inward from anouter edge of the brake disc to prevent a distance between the receiverand the transmitter from varying widely and thereby assure stability ofthe receiver in receiving the signal from the transmitter, and thereceiver is provided with a vehicle wheel speed detector which detects avehicle wheel speed.
 2. A tire information detecting device according toclaim 1, wherein the receiver is mounted at a linking member supportinga hub.
 3. A tire information detecting device according to claim 1,wherein the transmitter is mounted at a wheel rim supporting the tire.4. A tire information detecting device according to claim 1, wherein thedetector, the transmitter and the receiver are mounted at a drivenwheel.
 5. A tire information detecting device according to claim 4,wherein the receiver is disposed radially inward from an outer edge of ahub.
 6. A tire information detecting device according to claim 1,wherein the detector is included in the transmitter.
 7. A tireinformation detecting device according to claim 1, wherein thetransmitter includes a signal modulator which modulates the signal, andthe receiver includes a signal demodulator which demodulates the signal.8. A tire information detecting device according to claim 1, wherein thevehicle wheel speed detector is integrally formed with the receiver. 9.A tire information detecting device according to claim 1, wherein thereceiver is mounted on a linking member at the vehicle body side.
 10. Atire information detecting device comprising: a detector which detectsat least one of an air pressure, an air temperature in the tire, avehicle wheel acceleration and a power supply voltage supplied to thedetector; a transmitter which transmits a signal outputted from thedetector; a receiver which receives the signal transmitted from thetransmitter, the receiver being mounted at a vehicle body side; and adrum brake adjusted to apply a braking force to a vehicle, wherein thereceiver is positioned radially inward from an outer edge of the drumbrake to prevent a distance between the receiver and the transmitterfrom varying widely and thereby assure stability of the receiver inreceiving the signal from the transmitter, and the receiver is providedwith a vehicle wheel speed detector which detects a vehicle wheel speed.11. A tire information detecting device comprising: a detector whichdetects an air temperature in a tire; a transmitter which transmits asignal outputted from the detector; a receiver which receives the signaltransmitted from the transmitter, the receiver being mounted at avehicle body side; and a brake disc adjusted to apply a braking force toa vehicle, wherein the receiver is positioned radially inward from anouter edge of the brake disc to prevent a distance between the receiverand the transmitter from varying widely and thereby assure stability ofthe receiver in receiving the signal from the transmitter, and thereceiver is provided with a vehicle wheel speed detector which detects avehicle wheel speed.
 12. A tire information detecting device accordingto claim 11, wherein the receiver is mounted at a linking membersupporting a hub.
 13. A tire information detecting device according toclaim 11, wherein the transmitter is mounted at a wheel rim supportingthe tire.
 14. A tire information detecting device according to claim 11,wherein the detector, the transmitter and the receiver are mounted at adriven wheel.
 15. A tire information detecting device according to claim14, wherein the receiver is disposed radially inward from an outer edgeof a hub.
 16. A tire information detecting device according to claim 11,wherein the detector is included in the transmitter.
 17. A tireinformation detecting device according to claim 1, wherein thetransmitter and the receiver communicate via radio waves.
 18. A tireinformation detecting device according to claim 10, wherein thetransmitter and the receiver communicate via radio waves.
 19. A tireinformation detecting device according to claim 11, wherein thetransmitter and the receiver communicate via radio waves.